At its upstream end, a turbojet has an air inlet feeding both a fan and a compressor having blades that are carried by disks secured to a shaft that extends over a major fraction of the turbojet and that is driven in rotation by a turbine of the turbojet.
A nose cone is mounted on the upstream end of the shaft so that a fraction of the flow of air that penetrates inside the turbojet is deflected towards the blades of the fan, the flow then being separated into a primary flow which passes through an admission orifice of the compressor, and into a secondary flow which flows around the compressor, and which is then mixed with the primary flow, and/or feeds cooling circuits for cooling components of the turbojet.
In the prior art, the nose cone is mounted in stationary manner on the end of the shaft, and its shape and its dimensions are determined so as to optimize the angles of incidence of the air at the roots of the fan blades for a given flight stage.
The shape and the dimensions of the nose cone are also determined so as to provide protection against the ingestion of ice and of solid objects or particles.
The shape and dimensions chosen for the nose cone are therefore the result of a compromise between those two relatively contradictory constraints, and they therefore do not really satisfy either of those two constraints.